1. Field of the Invention
This invention relates to a liquid crystal display apparatus.
2. Discussion of the Prior Art
In general, large scale electronic signs employ either incandescent lights or magnetically manipulated elements for forming a variety of patterns or displays. Incandescent lights consume large quantities of power, and both of the systems require massive supporting structures. The net results is that both types of systems are somewhat expensive. The present inventors have found that an at least equally effective and much less expensive alternative resides in a liquid display apparatus.
Liquid display apparatuses are by no means new. Examples of such apparatuses are found, for example in Canadian Pat. Nos. 994,890, which issued to Gordon W. Hickman on Aug. 10, 1976 and 1,050,642, which issued to Werner E. L. Haas et al on Mar. 13, 1979, and U.S. Pat. Nos. 4,212,010, which issued to Karl H. Walter on July 8, 1980 and 4,408,836, which issued to Masayuki Kikuno on Oct. 11, 1983. The patented inventions are typical of the art in the field of the present invention. The patented inventions rely on separate controls for actuating separate display elements, or on matrix systems, in which rows and columns of a conductor matrix are actuated to switch liquid crystals between different optical states. Perhaps the most interesting of the patents (from the point of view of the present inventors) is the Kikuno U.S. Pat. No. 4,408,836 which teaches the use of a plurality of individual and discrete liquid display cells each having two plates which are perpendicular to each other to form extensions for overlapping portions of adjacent cells.
Problems inherent to the Kikuno and other prior art devices are dark areas, i.e. areas containing conductors or other hardware which results in a discontinuous display. If liquid display crystals are to be used in large assemblies such as advertising signs, it is important that the whole visible portion of the sign be usable, i.e. that the pattern or letters being displayed be shadow free. It has been found that this problem is not solved by the prior art devices.
The object of the present invention is to overcome the problems experienced with existing display systems by providing a relatively simple liquid crystal display apparatus, which is inexpensive to produce, and which can be used to produce clear patterns for displays in large scale electronic signs.